Is Putnam's 'brain in a VAT' hypothesis self-refuting?

Abstract

In this paper, I provide a detailed analysis of Putnam's conclusion (derived from the externalist interpretation of meaning and mental content) that the skeptical hypothesis, according to which we have always been brains in vats, is self-refuting. I confine my attention to the following question: If we assume that semantic externalism is plausible on independent grounds, does it follow that the semantic argument against skepticism (as articulated by Putnam) is indeed successful? In the first section, I briefly review the basic contention of Putnam's semantic externalism. In the second section, I outline and reexamine Putnam's, Brueckner's, and Warfield's version of the semantic argument. I hope to show that Putnam's version of this argument remains on a purely meta-linguistic level, which means that it can only prove that the phrase 'We are brains in a vat' must be false when it is considered in the context of the argument, although it most certainly does not prove that we are not brains in a VAT after all. In the third section, I argue that Brueckner's and Warfield's attempt to modify Putnam's argument, and consequently provide an a priori proof that we are not brains in a VAT, are ultimately unsuccessful, for both attempts beg the question against the skeptic. In the final section, I draw a comparison between the skeptical hypothesis and other cases of self-refuting statements and conclude that Putnam was ultimately right in claiming that the skeptical hypothesis is self-refuting in a weak sense, in which it is unassertible, although it might be true nevertheless.